Abrasive grain and grindstone

Abstract: An abrasive grain 1 includes a crystal defect CD in its crystal structure CS. The crystal defect CD is formed by a laser irradiation. (end of abstract)

Agent: Oblon, Spivak, Mcclelland, Maier & Neustadt, P.C. - Alexandria, VA, US
Inventors: Hiroshi Morita, Tomoyuki Kasuga, Shinji Soma
USPTO Applicaton #: #20060111031 - Class: 451540000 (USPTO)
Related Patent Categories: Abrading, Rigid Tool

Abrasive grain and grindstone description/claims

The Patent Description & Claims data below is from USPTO Patent Application 20060111031, Abrasive grain and grindstone.

Brief Patent Description - Full Patent Description - Patent Application Claims

INCORPORATION BY REFERENCE

[0001] The present application claims priority under 35 U.S.C. .sctn.119 to Japanese Patent Applications No. 2004-274352, filed on Sep. 22, 2004 and No. 2005-090303, filed on Mar. 28, 2005. The contents of that application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to an abrasive grain and a grindstone using plural number of the abrasive grain which performs self dressing function appropriate for grinding.

[0004] 2. Discussion of the background

[0005] Where a conventional grindstone grinds a workpiece made from iron material, ceramic material or etc., plural number of a hard abrasive grain, for example diamond or cubic boron nitride (CBN), is used for the grindstone. The grindstone is made from the steps of mixing the abrasive grains and vitrified bond or the like, and sintering the mixture. As shown in FIG. 5(a), a grinding wheel 100 is constructed from a core 103 and the grindstone (the abrasive grains 101 and the bond 102) glued on the circumference of the core 103. One part of each grain 101 crops out on the surface 100a of the grindstone and its surface is previously formed into microscopic roughness working as cutting edges 104 by a dresser, for example rotary diamond dresser (not shown).

[0006] Where the grinding wheel 100 includes the abrasive grains 101 whose diameter is comparative large (for example #80 to #120), each cutting edge 104 is worn and flattened due to the contact with the workpiece in the sequential grinding, thereby a flat surface 101a appears, as shown in FIG. 5(b). In the case of continuing to grind in such situation, because the grinding resistance increases between the workpiece and each surface 101a of the abrasive grains, grinding burn may occur and the grinding quality may deteriorate. To avoid the grinding burn, the dresser is used for deforming the flattened grains 101 to the microscopic roughness, thereby the cutting edges 104 are regenerated and the sequential grinding would be resumed.

[0007] However, where the grinding wheel 100 grinds the workpiece made from a hard material such as quenching steel, the abrasive grains 101 are remarkably worn. The grain 101 of diamond or CBN is too hard to perform self dressing function which regenerates the cutting edges 104 on its own surface due to the crack generated by the grinding load. Therefore, the grinding wheel 100 requires the dressing in advance and before the surface of the grain is flattened in the sequential grinding, thereby there may increase the cost related to the dressing.

[0008] Further, in case that the grinding wheel 100 has hard abrasive grains 101 and strong bond 102, the diamond grains of the dresser may be damaged during the dressing. Thus, the dressing condition must be set particularly.

SUMMARY OF THE INVENTION

[0009] In view of the foregoing, it is an object of the present invention to provide an abrasive grain which performs self dressing function even though the grain is hard, for example diamond or CBN, and to provide a grindstone having such abrasive grains. In order to achieve the above and other objects, an aspect of the present invention provides an abrasive grain of which crystal structure has one ore more crystal defect or microscopic gap formed by irradiation of laser. Second aspect of the present invention provides a grindstone comprising plural grains of which crystal structure has one or more crystal defect or microscopic gap formed by irradiation of laser.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiments when considered in connection with the accompanying drawings, in which:

[0011] FIG. 1 is a schematic illustration of a grinding wheel having abrasive grains of first embodiment related to the invention;

[0012] FIG. 2 is a schematic illustration of an example of irradiating the crystal structure of the abrasive grain of the first embodiment with a laser;

[0013] FIG. 3 is a schematic illustration of a self dressing function of the abrasive grains of the first embodiment;

[0014] FIG. 4 is a schematic illustration of further example of irradiating the grinding wheel related to the present invention with the laser;

[0015] FIG. 5 is a schematic illustration of a conventional dressing process;

[0016] FIG. 6 is a schematic illustration of a grinding wheel of second embodiment related to the invention;

[0017] FIG. 7 is a schematic illustration of a grinding wheel of third embodiment related to the invention; and

[0018] FIG. 8 is a schematic illustration of a grinding wheel of forth embodiment related to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An abrasive grain related to the present invention is inorganic or ceramic compound, for example diamond or cubic boron nitride (CBN). The grain has a strong and stable crystal structure so as to be very hard. For example, diamond is known as the hardest material whose crystal structure constructs a 3-D stable adamantane due to sp3 hybridised orbitals of electrons in their outer-most shell. On the other hand, CBN is known as comparison of diamond and is used for grinding tool or cutting tool. CBN has cubic crystal structure which is constructed by the regular connection between atoms of boron and nitrogen.

Brief Patent Description - Full Patent Description - Patent Application Claims
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